Tag and seal employing a micromachine artifact

ABSTRACT

A tamper resistant seal including a population of particles embedded in an adhesive, the population including at least one micromachine artifact of a predetermined physical shape.

GOVERNMENT INTERESTS

Embodiments of the invention were developed under Contract No.DE-AC04-94AL85000 between Sandia Corporation and the U.S. Department ofEnergy. The United States Government has certain rights in thisinvention.

TECHNICAL FIELD

Embodiments of the invention are in the field of physical object tagsand tamper indicators and more particularly relate to tags and sealsemploying a micromachine artifact for tamper resistant identification ofobjects.

BACKGROUND

Reflective Particle Tag (RPT) technology is in use for physicalauthentication of a tagged item. Generally, conventional RPT technologyentails a field-applied tag, such as a bar code, and a seal composed ofa random distribution of specular mineral particles, such as hematite,embedded in an adhesive. When illuminated from different angles, a RPTpresents complex patterns of millimeter-scale light reflections uniqueto the tag. Generally, an RPT procedure entails measuring referencereflected light patterns upon field application of the seal which arerecorded in association with the tag (e.g., bar code) to a referencedatabase. Subsequent authentication then entails remeasuring the lightreflecting patterns of the seal and comparing the patterns to thoserecorded for the tag in the reference database. A mismatch is indicativeof seal tampering, for example where a seal is broken to access anitem's contents or to relocate the tag to another item.

Advances in imaging and computing technology have permitted automationof the RPT procedure, enable greater inspection efficiency and wideradoption by various regulatory authorities. Techniques to increase theuniqueness of an RPT, for identifying the source of a RPT for example,and/or to provide additional protection against sophisticated methods oftampering, such as bisection and delamination, are thereforeadvantageous.

SUMMARY OF THE DESCRIPTION

The tag technology described herein imparts a predetermined physicaluniqueness to at least a subset of particles embedded in an adhesive. Inthe exemplary embodiment, at least one, and advantageously more thanone, micromachine artifact is included in the population of particleswhich are embedded in the adhesive. As such, one or more of a physicalstructure, a count, or a relative location, of the one or moremicromachine artifacts may be associated with a particular seal toprovide a basis for identifying the seal itself (e.g., the seal iscataloged based on a key derived from the physical shape(s) of themicromachine artifacts), identifying a source/origin of a seal, oridentifying an attempt at tampering with seal.

In an embodiment, a RPT includes a population of particles, a firstsubset of which are specularly reflective, and a second subset of whichare micromachine artifacts having a predetermined physical shape. Thefirst and second subsets of the particle population may be randomlydistributed in an adhesive matrix. Depending on the embodiment, themicromachine artifacts may contribute to a reflective signature of thetag. In embodiments, the micromachine artifacts have a criticaldimension no great than 500 microns.

In an embodiment, a frame is embedded in the adhesive matrix. The framemay be of a contiguous material which forms a perimeter surrounding thepopulation of particles. For example, the frame may be monocrystallineand include alignment marks integrally formed into the frame material.

Embodiments include application and measurement of a tag including amicromachine artifact embedded in an adhesive. In an exemplaryembodiment, measurement includes illuminating a portion of the sealcontaining a population of particles embedded in an adhesive matrix, thepopulation including at least one micromachine artifact of apredetermined shape, collecting image data from the illuminated portionof the seal, and executing an optical pattern recognition algorithm onthe image data to identify any artifact matching the at least onepredetermined shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not limitation, in the figures of the accompanying drawings inwhich:

FIG. 1A is a plan view of a tamper resistant seal including a pluralityof particles, at least one of which is a micromachine artifact, embeddedin an adhesive, in accordance with an embodiment;

FIG. 1B is an expanded view of the plan view illustrated in FIG. 1A;

FIG. 1C is a plan view of a tamper resistant seal including a framesurrounding at least one micromachine artifact embedded in an adhesive,in accordance with an embodiment;

FIG. 2 illustrates a plan view of a micromachine artifact which isembedded in an adhesive, in accordance with an embodiment;

FIG. 3A illustrates a plan view of a micromachine artifact which isembedded in an adhesive, in accordance with an embodiment;

FIG. 3B illustrates a cross-section view of the micromachine artifactillustrated in FIG. 3A, in accordance with an embodiment;

FIG. 4A illustrates a plan view of a frame which is embedded in anadhesive; in accordance with an embodiment;

FIG. 4B illustrates a cross-sectional view of the frame illustrated inFIG. 5A, in accordance with an embodiment;

FIG. 5A illustrates a plan view of an object surface to which a tamperresistant seal is to be applied, in accordance with an embodiment;

FIG. 5B illustrates a plan view of a tamper resistant seal having amicromachine artifact adhered to the object surface illustrated in FIG.5A, in accordance with an embodiment;

FIG. 5C illustrates a plan view of the tamper resistant seal illustratedin FIG. 5B with a population of particles including at least onemicromachine artifact embedded in an adhesive, in accordance with anembodiment;

FIG. 5D illustrates an expanded view of the tamper resistant sealillustrated in FIG. 5C showing a first micromachine artifact embedded ata first location in an adhesive, in accordance with an embodiment;

FIG. 5E illustrates an expanded view of the tamper resistant sealillustrated in FIG. 5C showing a second micromachine artifact embeddedat a second location in an adhesive, in accordance with an embodiment;

FIG. 5F illustrates an expanded view of the tamper resistant sealillustrated in FIG. 5C showing a discontinuity in a frame surroundingthe population of particles, in accordance with an embodiment;

FIG. 6A is a flow diagram illustrating a method of applying a tamperresistant seal having at least one micromachine artifact embedded in anadhesive, in accordance with an embodiment;

FIG. 6B is a flow diagram illustrating a method of recording positionalinformation for a micromachine artifact embedded in an adhesive, inaccordance with embodiments;

FIG. 6C is a flow diagram illustrating a method of authenticating atamper resistant seal having at least one micromachine artifact embeddedin an adhesive, in accordance with an embodiment;

FIG. 7A illustrates a schematic of an apparatus for automaticallyauthenticating a tamper resistant seal having at least one micromachineartifact embedded in an adhesive, in accordance with an embodiment; and

FIG. 7B illustrates a computer system for executing one or more of thealgorithms to authenticate a tamper resistant seal having at least onemicromachine artifact embedded in an adhesive, in accordance with anembodiment.

DETAILED DESCRIPTION

In the following description, numerous details are set forth. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without these specific details. In some instances,well-known methods and devices are shown in block diagram form, ratherthan in detail, to avoid obscuring the present invention. Referencethroughout this specification to “an embodiment” means that a particularfeature, structure, function, or characteristic described in connectionwith the embodiment is included in at least one embodiment of theinvention. Thus, the appearances of the phrase “in an embodiment” invarious places throughout this specification are not necessarilyreferring to the same embodiment of the invention. Furthermore, theparticular features, structures, functions, or characteristics may becombined in any suitable manner in one or more embodiments. For example,a first embodiment may be combined with a second embodiment anywhere thetwo embodiments are not mutually exclusive alternatives.

Generally, whereas for conventional RPT the specular particlesthemselves are of random physical shapes which are not predetermined,the tag technology described herein imparts a predetermined physicaluniqueness to at least a subset of the particles embedded in anadhesive. In the exemplary embodiment, at least one, and advantageouslymore than one, micromachine artifact is included in the population ofparticles which are embedded in the adhesive. As such, whereas only thelight reflecting patterns of the aggregate population of the particles,as applied in the field, imparts an identifiable characteristic to aconventional RPT seal, in the tag technology described herein, one ormore of a physical structure, a count, or a relative location, of theone or more micromachine artifacts is associated with a particular seal.The micromachine artifact may then provide a basis for identifying theseal itself (e.g., where the seal or tag is cataloged by a key fieldderived from the physical shape(s) of the micromachine artifacts),identifying a source/origin of a seal/tag, or identifying an attempt attampering with a seal/tag.

FIG. 1A is a plan view of a tamper resistant seal 100 including apopulation of particles 105, at least one of which is a micromachineartifact 110, embedded in an adhesive 101, in accordance with anembodiment. As illustrated, the tamper resistant seal 100 has beenapplied to a target object (not depicted). The adhesive 101 is to form amatrix surrounding the particle population 105, permanently fixing theirrelative location within the seal and permanently adhering them to asurface of the target object. The adhesive 101 is curable into amaterial which is transparent to light, preferably in the visible band,so that the particles may be readily illuminated and imaged. Inembodiments, the adhesive 101 is a thermoplastic which may further beUV-curable. In exemplary embodiments, the adhesive 101 is an opticallytransparent acrylic resin, such as polymethyl methacrylate (PMMA).

FIG. 1B is an expanded view of the plan view illustrated in FIG. 1A. Asshown in FIG. 1B, the particle population 105 includes a plurality ofparticles, at least one of which is micromachine artifact 110 having apredetermined physical shape. The particle population 105 is randomlydistributed within the adhesive 101. While in certain embodiments, theentire particle population 105 may consist only of micromachineartifacts, for the exemplary embodiment the particle population 105further includes particles 115 which have no predetermined shape. Theparticles 115 having no predetermined physical shape may be randomlyshaped or otherwise form a non-identifiable, generic population ofparticles. In the exemplary RPT embodiment, the particles 115 arespecularly reflective particles. The specularly reflective particles maybe a mineral, such as hematite, for example, prepared in any mannerknown in the art. The particles 115 may take other forms as well for RPTor non-RPT embodiments. For example, where other optical phenomena areutilized, such as polarization, etc., the particles 115 may bemacromolecules known in the art to impart, as a population, anidentifiable polarization characteristic to the seal.

At least one micromachine artifact 110 is included in the tamperresistant seal 100. As further shown in FIG. 1B, a plurality ofmicromachine artifacts 110A, 110B, 110C and 110D having distinctphysical shapes may be embedded in the adhesive 101 to form the singletamper resistant seal 100. For embodiments described herein, amicromachine artifact is a particle which has been patterned into apredetermined shape having at least one length, referred to herein ascritical dimension (CD), that is no greater than 500 micrometers (μm).In certain embodiments, the micromachine artifact is smaller than 500 μmin all dimensions. The micromachine artifacts may generally be in anyshape or form known in the art and manufactured by any in the vast arrayof microelectronic and microelectromechanical (MEM) techniques known inthe art. Exemplary subtractive techniques include reactive ion etching,wet chemical etching, polishing, and ion beam milling while exemplaryadditive techniques include chemical vapor deposition (CVD) and physicalvapor deposition, either of which may be plasma enhanced.

With the micromachine artifact 110 having a predetermined shape, it maybe made relatively complex to manufacture and therefore difficult and/orexceedingly expensive to mimic. Either a micromachine artifact'sphysical shape or physical location within the adhesive matrix, or both,may further provide a basis for identifying the seal. For example, acombination of at least three structurally distinct micromachineartifacts may be included in the particle population 105, each micromachine artifact type having a different predetermined shape. A sourceof the seal may then be associated with a library of tens or hundreds ofmicromachine artifact shapes from which each of the plurality artifactsmay be selected to identify a particular seal. A pre-mixed batch ofparticles may be provided for field application of each seal. Thepre-mixed batch of particles may include a plurality of each physicallydistinct artifact. For example, ten artifacts of a first shape may bemixed with ten artifacts of a second shape and ten artifacts of thirdshape. The artifact mixture may then be further mixed with particles ofan undetermined shape to form the particle population 105. Uponapplication of the particle population to an object, the combination ofmicromachine artifact types may then be utilized to identify or catalogthe seal in a manner which is physically unique (as opposed to a barcode which is typically only cataloged as logically unique).

In embodiments, the micromachine artifact 110 is a monocrystalline orpolycrystalline semiconductor material, such a silicon, germanium, orgroup III and group V elements, and there alloys. In other embodimentsthe micromachine artifact 110 is a thin film delaminated from anarbitrary substrate. For such embodiments, the thin film may further bean amorphous material, such as silicon dioxide, or metallic film, suchas copper, etc.

FIG. 2 illustrates an expanded plan view of micromachine artifacts 110A,11B and 110C from FIG. 1B. In some embodiments, the micromachineartifact includes a plurality of repeating features along an outer edgeof the micromachine artifact, each repeating feature having a criticaldimension no greater than 500 μm. In one exemplary embodiment,micromachine artifact 110A has a longest length, M₁, extending in thex-dimension and is shaped into a gear have a plurality of teeth 111 and112. In a first embodiment, the longest length M₁ is no greater than 500μm and therefore the teeth 111, 112 define a CD substantially smallerthan 500 μm (e.g., hundreds of nanometers to tens of μm). In analternate embodiment, the longest length M₁ is greater than 500 μm, withthe teeth 111, 112 defining a CD no greater than 500 μm. Themicromachine artifact need not have a highly complex shape and incertain embodiments is a simple polygon. For example, in anotherexemplary embodiment, micromachine artifact 110B is a hexagon having alongest length M₂ in the x and y dimensions with each side 113, 114having a length defining a CD. In a first embodiment, the longest lengthM₂ is no greater than 500 μm and therefore the sides 113, 114 define aCD substantially smaller than 500 μm (e.g., hundreds of nanometers totens of μm). In an alternate embodiment, the longest length M₂ isgreater than 500 μm, with the sides 113, 114 defining a CD no greaterthan 500 μm.

In still another embodiment illustrated in FIG. 3A, a hexagon having alongest length M₃ greater than 500 μm, and sides 113, 114 also greaterthan 500 μm includes plurality of repeating features 117 and 118 formedon a side 116 of the micromachine artifact 110C. Each repeating feature117, 118 has a critical dimension no greater than 500 μm. FIG. 3Billustrates a cross-section view along the a-a′ line of the micromachineartifact 110C illustrated in FIG. 3A, in accordance with an embodiment.As shown, the micromachine artifact 110C has a predetermined physicalthickness T₁ (along the z-axis) which is less than a longest length M₃of the artifact (in the x or y-axis). Thicknesses less than the longestlength may be advantageous in certain applications where mechanicalfragility is desirable as a means of tamper detection, as describedfurther elsewhere herein. For exemplary embodiments which employmicromachine artifacts of single crystalline silicon, the thickness T₁will typically be between 50-800 μm as the micromachine artifacts willgenerally be formed from silicon wafers.

FIG. 1C is a plan view of a tamper resistant seal 140 including a frame150 surrounding the particle population 105 embedded in an adhesivematrix, in accordance with an embodiment. The frame 150 may be added tothe tamper resistant seal 140 (e.g., adhered and/or embedded into theadhesive 101 before or after particle population 105 is embedded in theadhesive 101) to arrive at the tamper resistant seal 140. Inembodiments, the frame 150 may function as a means of identification,pattern recognition alignment, and tamper detection, as furtherdescribed herein. In an embodiment, the frame 150 is a continuousmaterial, formed of any of the materials described for the micromachineartifact 110. In further embodiments, the frame 150 includesmicromachine features having a CD less than 500 μm forming reliefs alongan edge or into a top or bottom surface of the frame 150.

FIG. 4A illustrates a plan view of a frame which is to be embedded in anadhesive, in accordance with an embodiment, while FIG. 4B illustrates across-sectional view of the frame 150 along the b-b′ line. As shown inFIG. 4A, the frame 150 spans a longest length (e.g., diameter) M4 havingannular shape with a frame width W₁. As illustrated in FIG. 1C, theframe 150 is to span a macroscopic portion of a seal and therefore M₁may be of virtually any dimension, limited in the exemplary embodimentwhere the frame 150 is a contiguous piece of single crystallinesemiconductor, to the diameter of a silicon ingot (e.g., 200, 300, 450mm, etc.). To accommodate handling and application in the field, theframe width W₁ may be selected to have sufficient mechanical strengthwhich may further be a function of M₁. Exemplary frame widths arebetween a few thousand microns (μm) to tens of millimeters. The frame150 has a thickness T₂ (FIG. 4B) which may be in the thickness rangedescribed for the micromachine artifact 110 (e.g., a few hundred to lessthan a thousand micron).

In an embodiment, the frame 150 includes alignment fiducials 155, 156integrally formed into the frame material, for example by any of thefabrication techniques described for the micromachine artifact 110. Thealignment fiducials 155, 156 may take any form conventional in the artfor automated, machine-based pattern recognition algorithms and are toprovide a translational and/or rotational frame of reference embeddedwithin a tamper resistant seal (e.g., tamper resistant seal 100) towhich image data generated by optical scans of the seal may bereferenced and cataloged to a database.

FIG. 5A illustrates a plan view of an object to which a tamper resistantseal is to be applied, in accordance with an embodiment. The objectincludes component surfaces 500 and 501 separated by the void 509.Affixing the component 500 to component 501 is a screw surface 505having a hex shaped void 507 (e.g., hex-wrench screw). FIG. 6A is a flowdiagram illustrating a method 601 for applying a tamper resistant sealhaving at least one micromachine artifact embedded in an adhesive to anobject, such as that illustrated in FIG. 5A, in accordance with anembodiment. At operation 610, an adhesive is applied to an objectsurface. At operation 615 at least one micromachine artifact is applied.In exemplary embodiment illustrated in FIG. 5B, a hex-shapedmicromachine artifact 110C, is adhered with adhesive 101A to the screwsurface 505 to span the hex shaped void 507 (e.g., longest length M₃greater than a millimeter). The micromachine artifact 110C may beprocessed to be non-reflective to mimic the physical appearance of thehex shaped void 507 and be somewhat hidden.

Returning to FIG. 6, a particle population 105 (see FIG. 5C) may then berandomly distributed in adhesive over a portion of the seal at operation620. In reference to the exemplary embodiment illustrated in FIG. 5C,the particle population 105 may, for example, be applied at operation620 either as a suspension in uncured adhesive 1019 or physicallyincorporated after the uncured adhesive 101B is applied to the componentsurface 500 and 501. As illustrated, a portion of the particlepopulation 105 is disposed over the hex-shaped micromachine artifact110C to further obscure the physical barrier presented by artifact 110C.As further illustrated by the expanded views in FIGS. 5D and 5E, theparticle population 105 may also include at least one micromachineartifact 110A, 110B as well as other particles of unknown shape 115,either or both of which may be specularly reflective. Due to relativelylarge physical size, concealment, and mechanical fragility, micromachineartifact 110C is susceptible to fracture in response to tag defeatattempts. For the micromachine artifacts 110C which include uniquefeatures (117 and 118 in FIG. 3A), imitation is difficult.

Returning to FIG. 6A, a frame is applied at operation 625. In theexemplary embodiment of FIG. 5C, the frame 150 is embedded in theuncured adhesive 101B before or after embedding the particle population105 and/or the micromachine artifact into the uncured adhesive. As shownin FIG. 5C, the frame 150 is positioned to span the void 509. Theadhesive is then cured to affix the particles and frame to the componentsurfaces 500, and 501. Method 601 completes with mapping the artifacts'positional data at operation 630. For RPT embodiments, sparkle data forthe particle population 105 may be further collected using techniquesknown in the art.

FIG. 6B is a flow diagram illustrating a method 602 for mappingpositional information of a micromachine artifact embedded in anadhesive, in accordance with embodiments. FIG. 7A illustrates aschematic of an apparatus for automatically performing the method 602.In a first embodiment, at operation 631, a portion of a seal containinga frame surrounding the population of particles (e.g., frame 150 in FIG.5C) is illuminated by light source 705 (FIG. 7A) through optics 706.Alignment fiducials 155, 156 are identified with a pattern recognitionalgorithm 711 executed by the computer processor 715. Upon successfulrecognition of the alignment fiducials 155, 156, a reference orientationfor the seal is then recorded to a memory or mass storage device 725 inthe reference database 715.

At operation 635, a portion of the seal containing the particlepopulation embedded in an adhesive matrix (e.g., particle population 105in FIG. 5C) is similarly illuminated and image data from particlepopulation collected with an image sensor 712, such as a CMOS camera.The computer processor 715 executes another pattern recognitionalgorithm 710 to analyze particle image data in search of physicalfeatures matching one or more predetermined shapes, which may forexample be accessed from artifact shape data 741 stored to the memory725. Any conventional edge or contrast based pattern recognitionalgorithms known in the art may be employed. Each micromachine artifactidentified as a match with one of the predetermined shapes is thenassociated with a relative position within the seal, in the firstembodiment relative to the alignment fiducials 155, 156. The position ofthe identified artifact (e.g., type 110A, or 110B, or 110C, etc.) isthen stored to memory 725 as artifact positional data 735. For an RPTembodiment, a reflected light pattern is measured and particle sparkledata 740 is further associated with the artifact positional data 735 andartifact identity (shape data 741) in the reference database 715.

In a second embodiment illustrated in FIG. 6B, at operation 632, aportion of the seal containing the population of particles isilluminated and image data is analyzed as described above, but inabsence of any positional reference provided by a frame fiducial (e.g.,for embodiments where no frame is incorporated into the seal). Uponidentifying a plurality of micromachine artifacts, a physical positionand/or orientation of first embedded artifact is referenced relative tosecond embedded artifact at operation 636. For embodiments where atleast three micromachine artifacts are identified at operation 632, theat least three artifacts may be related in two dimensional space toprovide a reference orientation and/or positional data 735 which maythen be stored along with artifact shape (identity) at operation 640.For an RPT embodiment, particle sparkle data 740 is further associatedwith the artifact positional data 735 and artifact shape data 741 in thereference database 715.

FIG. 6C is a flow diagram illustrating a method 603 for authenticating atamper resistant seal having at least one micromachine artifact embeddedin an adhesive, in accordance with an embodiment. At operation 650particles embedded in the adhesive are illuminated at operation 650 andimage data is collected at operation 655 and an optical patternrecognition algorithm is executed at operation 660, for examplesubstantially as described for method 602, and the tamper resistanceseal is analyzed against a reference database (e.g. based on areferenced artifact shape at operation 670 or a referenced artifactlocation at operation 680). The seal is then authenticated or tamperingidentified at operation 690 depending on the outcome of operations 670,680 (e.g., match or mismatch with reference record).

For embodiments where the micromachine artifacts serve to identify theseal, either or both of a shape (physical identity) or location of eachrecognized artifact may be utilized as a key field under which amatching record may be recovered for a particular seal previouslyrecorded to a database, such as reference database 715. For embodimentswhere other means identify the seal, for example where the seal includesa bar code, either or both of a shape (physical identity) or location ofeach recognized artifact may be utilized as a means to detect tamperingwith the seal. Changes in either a physical shape of a recognizedmicromachine artifact, a count of recognized micromachine artifacts, orlocation of recognized micromachine artifacts relative the artifactpositional data 735, and artifact shape data 741 recorded for aparticular seal may be automatically identified. For example, a locationof an artifact matching a first predetermined shape, relative to thealignment fiducial, is compared to a location previously associated witha micromachine artifact of the first predetermined shape in a databaserecord.

In embodiments, image data collected from a frame surrounding theparticle population may also be analyzed for evidence of tampering. Forembodiments where the frame 150 is micromachined to have uniquefeatures, the frame is both a fragile and difficult to mimic. Because ofthe physical fragility of the frame (e.g., single crystalline siliconhaving a diameter of centimeters and thickness of hundreds ofmicrometers), the frame is subject to fracture during seal bisectionattempts. For example, FIG. 5F illustrates an expanded view of the frame150, in accordance with an embodiment. A discontinuity 570 through theframe may be identified automatically with a pattern recognition routineused to process image data collected under sufficient magnification. Forsuch embodiments, any pattern recognition routines known in the art tobe sensitive to the image contrast resulting from the discontinuity 570may be employed.

For RPT embodiments, where the population of particles further compriserandomly distributed specularly reflective particles of a random shape,either of methods 601 and 603 may be augmented with any conventionalmethod for measuring a reflected light pattern from a tag's particlepopulation. Complex reflection data may be cataloged to a database inassociation with any micromachine artifacts identified in the tag and/orin association with a tag frame (e.g., frame 150). Authentication and/ortamper detection may then be further premised on a comparison of ameasured reflected light pattern with a reference reflected lightpattern.

FIG. 7B illustrates a computer system 700 within which a set ofinstructions, for causing the machine to execute one or more of thealgorithms discussed herein may be executed, for example to analyze areflected light from a tag to identify at least one micromachineartifact. The exemplary computer system 700 includes a processor 702, amain memory 704 (e.g., read-only memory (ROM), flash memory, dynamicrandom access memory (DRAM) such as synchronous DRAM (SDRAM) or RambusDRAM (RDRAM), etc.), a static memory 706 (e.g., flash memory, staticrandom access memory (SRAM), etc.), and a secondary memory 718 (e.g., adata storage device), which communicate with each other via a bus 730.

Processor 702 represents one or more general-purpose processing devicessuch as a microprocessor, central processing unit, or the like. Moreparticularly, the processor 702 may be a complex instruction setcomputing (CISC) microprocessor, reduced instruction set computing(RISC) microprocessor, very long instruction word (VLIW) microprocessor,processor implementing other instruction sets, or processorsimplementing a combination of instruction sets. Processor 702 may alsobe one or more special-purpose processing devices such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), a digital signal processor (DSP), network processor, or thelike. Processor 702 is configured to execute the processing logic 726for performing the operations and steps discussed herein.

The computer system 700 may further include a network interface device708. The computer system 700 also may include a video display unit 710(e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), analphanumeric input device 712 (e.g., a keyboard), a cursor controldevice 714 (e.g., a mouse), and a signal generation device 716 (e.g., aspeaker).

The secondary memory 718 may include a machine-accessible storage medium(or more specifically a computer-readable storage medium) 731 on whichis stored one or more sets of instructions (e.g., software 722)embodying any one or more of the methodologies or functions describedherein. The software 722 may also reside, completely or at leastpartially, within the main memory 704 and/or within the processor 702during execution thereof by the computer system 700, the main memory 704and the processor 702 also constituting machine-readable storage media.The software 722 may further be transmitted or received over a network720 via the network interface device 708.

The machine-accessible storage medium 731 may also be used to storepattern recognition algorithms, artifact shape data, artifact positionaldata, or particle sparkle data. While the machine-accessible storagemedium 731 is shown in an exemplary embodiment to be a single medium,the term “machine-readable storage medium” should be taken to include asingle medium or multiple media (e.g., a centralized or distributeddatabase, and/or associated caches and servers) that store the one ormore sets of instructions. The term “machine-readable storage medium”shall also be taken to include any medium that is capable of storing orencoding a set of instructions for execution by the machine and thatcause the machine to perform any one or more of the methodologies of thepresent invention. The term “machine-readable storage medium” shallaccordingly be taken to include, but not be limited to, solid-statememories, and optical and magnetic media.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. Although the present invention has been describedwith reference to specific exemplary embodiments, it will be recognizedthat the invention is not limited to the embodiments described, but canbe practiced with modification and alteration. Accordingly, thespecification and drawings are to be regarded in an illustrative senserather than a restrictive sense.

What is claimed is:
 1. A tamper resistant seal, comprising: an adhesivematrix; a population of particles embedded in the adhesive matrix,wherein the population includes at least one particle that is amicromachine artifact formed by a microelectronic andmicroelectromechanical technique to have a predetermined physical shape;a frame embedded in the adhesive matrix, the frame being of a contiguousmaterial which forms a perimeter surrounding the population of particleswherein the micromachine artifact comprises a material selected from agroup consisting essentially of monocrystalline or polycrystallinesemiconductor material; and wherein the micromachine artifact comprisesa plurality of repeating features having a critical dimension of lessthan 500 μm.
 2. The tamper resistant seal of claim 1, wherein thephysical shape or physical location of the at least one micromachineartifact within the seal identifies the seal.
 3. The tamper resistantseal of claim 1, wherein the population of particles comprises at leastthree structurally distinct micromachine artifacts, each having adifferent predetermined shape, the combination of the at least threeartifacts identifying the seal.
 4. The tamper resistant seal of claim 1,wherein an outer edge of the at least one micromachine artifact includesthe plurality of repeating features, each repeating feature having aside with a critical dimension no greater than 500 μm.
 5. The tamperresistant seal of claim 1, wherein the predetermined physical shape isdefined in a first and second dimension and the artifact has apredetermined physical thickness in a third dimension which is less thana longest length of the artifact in the first or second dimension. 6.The tamper resistant seal of claim 5, wherein the predetermined shapecomprises a polygon, at least one side having a dimension smaller thanthe longest length.
 7. The tamper resistant seal of claim 1, wherein themicromachine artifact comprises at least one length greater than amillimeter.
 8. The tamper resistant seal of claim 1, wherein the frameis monocrystalline and includes alignment marks integrally formed intothe frame material.
 9. The tamper resistant seal of claim 1, wherein theadhesive comprises a UV-curable acrylic resin.
 10. The tamper resistantseal of claim 1, wherein the population of particles further compriserandomly distributed specularly reflective particles of a random shape.